For the Election of 1860, there were four candidates: Lincoln, Douglas, Breckinridge, and Bell. Why were there four main candidates in the election?

A. Both the Democratic and Republican parties became divided over the issue of slavery, and each had two nominees.
B. Southern and Northern Democrats could not agree on a cohesive platform or candidate.
C. Southern and Northern Republicans split over an argument about the Western territories.
D. In addition to the Democratic and Republican parties, there were also two smaller independent parties as candidates.

I believe it's A. If it's not, what is it and why?
AP United States History